Homework # 4 - NET 331 and net 221

1
NET331:
COMPUTER NETWORKS
FUNDAMENTALS
Networks and Communication
Department
Chapter # 23
Question 3
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Do port addresses need to be unique? Why or why
not ?Why are port addresses shorter than IP address
Port addresses do not need to be universally unique as long as each IP address
Port address pair uniquely identify a particular process running on a
particular host. A
Good example would be a network consisting of 50 hosts, each running echo
server software. Each server uses the well known port number 7, but the IP
address, together with the port number of 7, uniquely identify a particular
server program on a particular host.
Port addresses are shorter than IP addresses because their domain, a single
system, is smaller than the domain of IP addresses, all systems on the Internet.
Question 9
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Compare the TCP header and the UDP header. List the field in
the TCP header that are missing from UDP header. Give the
reason for the absence.
Question 10
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UDP is a message-oriented protocol. TCP is a byte-oriented
protocol. If an application needs to protect the boundaries
of its message, which protocol should be used, UDP or TCP?
UDP is preferred because each user datagram can be used for
each chunk of data.
Question 11
5
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a.
What can you say about the TCP segment in which the value of
the control field is one of the following
000000
None of the control bits are set. The segment is part of a data transmission
without piggybacked acknowledgment
a.
000001
The FIN bit is set. This is a FIN segment request to terminate the connection.
a.
010001
The ACK and the FIN bits are set. This is a FIN+ACK in response to a received
FIN segment
Question 14
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An SNMP client residing on a host with IP address 122.45.12.7
sends a message to an SNMP server residing on a host with IP
address 200.112.45.90.
What is the pair of socket used in this communication
The client would use the IP address 122.45.12.7, combined with
an ephemeral port number, for its source socket address
And the IP address 200.112.45.90, combined with the wellknown port number 161, as the destination socket address.
Question 16
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A client has a packet of 68,000 bytes. Show how this packet can
be transferred by using only one UDP user datagram
This datagram cannot be transferred using a single user
datagram.
Question 21
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An IP datagram is carrying a TCP segment destined for address
130.14.16.17/16. The destination port address is corrupted and
it arrive at destination 130.14.16.19/16.
How does the receiving TCP react to this error?
It looks as if both the destination IP address and the destination
port number are corrupted. TCP calculates the checksum and
drops the segment.
Question 26
9
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In a connection, the value of cwnd is 3000 and the value of rwnd
is 5000. The host has sent 2000 bytes which has not been
acknowledged. How many more bytes can be sent?
Window size= minimum (cwnd ,rwnd)
Window size = minimum (3000 , 5000)=3000
The number of bytes that can be sent =
3000 − 2000 = 1000 bytes
Question 27
10
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TCP opens a connection using an initial sequence number (ISN) of
14,534.The other party opens the connection with an ISN of
21,732.Show the three TCP segments during the connection
establishment.
Question 27 answer
11
Well-known port
17-Nov-14
Ephemeral port
Networks and Communication Department